如何制作cascade =“all，delete-orphan”的hibernate集合副本 [英] How to make a copy of hibernate collection with cascade="all,delete-orphan"

问题描述

  A a =（A）会话。 get（A.class，id）; 
 session.evict（a）; 
 a.setId（null）; 
 session.save（a）; 
  

然而，这并不奏效，我得到以下期待：

  org.hibernate.HibernateException：不要更改cascade =all-delete-orphan集合的引用：com.test.AB 
  

它可以安全地承担这个错误，因为我有一个在实体A中定义的B实体的集合：

 < list name =Btable =Blazy =falsecascade =all，delete-orphan> 
< key column =A_IDnot-null =true/> 
< index column =X/> 
 < / list> 
  

如何制作实体A的副本，包括实体B的集合而不休眠不满意？

解决方案

以前在我的项目中遇到同样的问题。

对我来说，它的工作原理是将list-entries的ID设置为null。

  //通过使用序列化复制一个aOriginal clone 
 a.setId（null）; 
 for（B b：a.getBs（））{
 b.setId（null）; 
} 
 session.save（a）; 
  

对于克隆本身，我使用 Apache SerializationUtils clone 。

原因是，hibernate试图复用已经存在的复制实体的列表条目。但是这个已经存在的列表条目被链接到一个原始实体。所以它试图在实体中改变列表本身，因为实体改变了。但是，如果用删除孤儿（只能修改列表中的条目，而不是列表本身）注释，则不能更改列表。所以引发异常。

如果我将list-entry-id设置为null，它们也会被插入newley。对象层次结构（而不​​是仅主要实体）被复制。所以豁免不再被抛出。

I am trying to make a copy of a hibernate entity A like this:

A a = (A) session.get(A.class, id);
session.evict(a);
a.setId(null);
session.save(a);

This however does not work and i get the following expetion:

org.hibernate.HibernateException: Don't change the reference to a collection with cascade="all-delete-orphan": com.test.A.B

Its safe to assume this error happens because of i have a collection of B entity defined in entity A:

<list name="B"  table="B" lazy="false" cascade="all,delete-orphan">
    <key column="A_ID" not-null="true"/>
    <index column="X"/>            
    <one-to-many class="com.test.B"/>
</list>

How is it possible to make a copy of entity A, including its collection of entitys B without hibernate being unhappy about it?

解决方案

I had the same problem previously in my project.

For me it works, to set the ID of the list-entries to null.

// make copy a of aOriginal by using serialisation clone 
a.setId(null);
for (B b : a.getBs()) {
    b.setId(null);
}
session.save(a);

For the clone itself I used the Apache SerializationUtils clone.

The reason is, that hibernate tries to "reuse" already persisted list-entries for the "copied" entity. But this already persisted list-entries are linked to a original entity. So it tries to "change" the list itself in the entity, because the entity changed. But you can't change the list if it is annotated with "delete-orphans" (you only can modify the entries of the list, but not the list itself). So the exception is thrown.

If I set the list-entry-IDs to null, they will also be inserted newley. And the object hierarchy (instead of only the main entity) is duplicated. So the exeption is no longer thrown.

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